X86: Avoid accessing SDValues after they've been RAUW'd

This fixes two use-after-frees in selectLEA64_32Addr. If matchAddress
matches an ADD with an AND as an operand, and that AND hits one of the
"heroic transforms" that folds masks and shifts, we end up with N
pointing to an SDNode that was deleted. Make sure we're done accessing
it before that.

Found by ASan with the recycling allocator changes in llvm.org/PR26808.

llvm-svn: 266130

1 files changed, 8 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 4105191147a..54c47011265 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1574,10 +1574,12 @@ bool X86DAGToDAGISel::selectMOV64Imm32(SDValue N, SDValue &Imm) {
 bool X86DAGToDAGISel::selectLEA64_32Addr(SDValue N, SDValue &Base,
                                          SDValue &Scale, SDValue &Index,
                                          SDValue &Disp, SDValue &Segment) {
+  // Save the debug loc before calling selectLEAAddr, in case it invalidates N.
+  SDLoc DL(N);
+
   if (!selectLEAAddr(N, Base, Scale, Index, Disp, Segment))
     return false;
 
-  SDLoc DL(N);
   RegisterSDNode *RN = dyn_cast<RegisterSDNode>(Base);
   if (RN && RN->getReg() == 0)
     Base = CurDAG->getRegister(0, MVT::i64);
@@ -1617,6 +1619,10 @@ bool X86DAGToDAGISel::selectLEAAddr(SDValue N,
                                     SDValue &Segment) {
   X86ISelAddressMode AM;
 
+  // Save the DL and VT before calling matchAddress, it can invalidate N.
+  SDLoc DL(N);
+  MVT VT = N.getSimpleValueType();
+
   // Set AM.Segment to prevent MatchAddress from using one. LEA doesn't support
   // segments.
   SDValue Copy = AM.Segment;
@@ -1627,7 +1633,6 @@ bool X86DAGToDAGISel::selectLEAAddr(SDValue N,
   assert (T == AM.Segment);
   AM.Segment = Copy;
 
-  MVT VT = N.getSimpleValueType();
   unsigned Complexity = 0;
   if (AM.BaseType == X86ISelAddressMode::RegBase)
     if (AM.Base_Reg.getNode())
@@ -1667,7 +1672,7 @@ bool X86DAGToDAGISel::selectLEAAddr(SDValue N,
   if (Complexity <= 2)
     return false;
 
-  getAddressOperands(AM, SDLoc(N), Base, Scale, Index, Disp, Segment);
+  getAddressOperands(AM, DL, Base, Scale, Index, Disp, Segment);
   return true;
 }